Someone started typing greetings on my screen, have I been hacked and what else can I do to prevent

I have reset my router, changed the username and password, checked my windows XP for updates, updated and scanned my Norton Antivirus, run ad-aware, reconfigured (reset) all my norton firewall settings, created a limited user account now. Anything else I should check for? Is there software to check for trojans (will Norton check?) and what about root kits? Any software I can use for this? Thanks!

Someone started typing greetings on my screen, have I been hacked and what else can I do to prevent it?nortan antivirus

VIRUS REMOVAL PROCESS:

do this OFFLINE

trash likes to hide in your restore system,so every time you clean up your computer and you use system restore,it restores the trash along with everything else !

turn off system restore:

XP:

start--all programs--accessories--system tools--system restore

check the off box

Vista:

right click computer icon

select properties

select system protection

uncheck os ( c: ) ( system )

alerter %26 messenger services:

stop messenger spam !!

XP only:

all programs--administrative tools--services

all services are in alphabetical order,right click both alerter %26 messenger services--select properties--from drop down menu,select disable

Active X:

XP ONLY

internet explorer--tools--internet options--security--advanced